看了一圈评论区，发现貌似没有人遇到和我相同的问题，特此记录一下。

环境：anaconda 下新建的环境 py39(python 3.9.4)，base 环境为 python 3.8.5，我一般都是在新建的环境下学习，运行requests.get报错：

>>> import requests
>>> r = requests.get('https://www.douban.com')
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "C:\Anaconda3\envs\py39\lib\site-packages\requests\api.py", line 76, in get
    return request('get', url, params=params, **kwargs)
  File "C:\Anaconda3\envs\py39\lib\site-packages\requests\api.py", line 61, in request
    return session.request(method=method, url=url, **kwargs)
  File "C:\Anaconda3\envs\py39\lib\site-packages\requests\sessions.py", line 542, in request
    resp = self.send(prep, **send_kwargs)
  File "C:\Anaconda3\envs\py39\lib\site-packages\requests\sessions.py", line 655, in send
    r = adapter.send(request, **kwargs)
  File "C:\Anaconda3\envs\py39\lib\site-packages\requests\adapters.py", line 439, in send
    resp = conn.urlopen(
  File "C:\Anaconda3\envs\py39\lib\site-packages\urllib3\connectionpool.py", line 696, in urlopen
    self._prepare_proxy(conn)
  File "C:\Anaconda3\envs\py39\lib\site-packages\urllib3\connectionpool.py", line 964, in _prepare_proxy
    conn.connect()
  File "C:\Anaconda3\envs\py39\lib\site-packages\urllib3\connection.py", line 359, in connect
    conn = self._connect_tls_proxy(hostname, conn)
  File "C:\Anaconda3\envs\py39\lib\site-packages\urllib3\connection.py", line 500, in _connect_tls_proxy
    return ssl_wrap_socket(
  File "C:\Anaconda3\envs\py39\lib\site-packages\urllib3\util\ssl_.py", line 432, in ssl_wrap_socket
    ssl_sock = _ssl_wrap_socket_impl(sock, context, tls_in_tls)
  File "C:\Anaconda3\envs\py39\lib\site-packages\urllib3\util\ssl_.py", line 474, in _ssl_wrap_socket_impl
    return ssl_context.wrap_socket(sock)
  File "C:\Anaconda3\envs\py39\lib\ssl.py", line 500, in wrap_socket
    return self.sslsocket_class._create(
  File "C:\Anaconda3\envs\py39\lib\ssl.py", line 997, in _create
    raise ValueError("check_hostname requires server_hostname")
ValueError: check_hostname requires server_hostname

解决办法：

1. (python 3.8.5 直接跳到第 2 步) 将默认的 urllib3 1.26.4 降级为 urllib3 1.25.11：

conda install urllib3==1.25.11

2. 再次运行requests.get，豆瓣的status_code为 418，百度、谷歌的status_code为 200：

>>> import requests
>>> r = requests.get('https://www.douban.com')
>>> r.status_code
418
>>> r = requests.get('https://www.baidu.com')
>>> r.status_code
200
>>> r = requests.get('https://www.google.com')
>>> r.status_code
200

3. 添加User-Agent，有值就行，具体值无所谓：

>>> r = requests.get('https://www.douban.com', headers={'User-Agent': 'M'})
>>> r.status_code
200
>>> r = requests.get('https://www.douban.com', headers={'User-Agent': 'A'})
>>> r.status_code
200